For a race that has long bedeviled the surface world, the gill-men remain mysterious. Any school child in the City knows the story of Horatio Stormalong who repelled the last incursion of the creatures, but the only modern account of them in their native habitat comes from the memoir of a journalist held hostage by the merman separatist and terrorist known as Nemo.
Nemo’s vessel seems to have been captured by the gill-men in the ocean’s depths and taken to a sunken ruin of ancient Meropis where the gill-men lived. Though this point was never entirely clear, it seems the gill-men consider themselves the descendants of the Meropisians. If this is true, the forces led to their smaller stature and inhuman appearance are mysterious.
Gill-men seem a distinct species from the sea devils, who are larger with toothier maws and may be (horribly) interfertile with humans. They also seem unrelated to whatever species the head of Thraug belongs too.
Nemo’s encounter with the gill-men shows they have made advances in technology since their last attempted invasion, even if not exactly at pace with humanity's. This fact, combined with their belligerence and organization, suggests the gill-men remain a potential threat to the surface world.
[Mechanically, treat the gill-men has aquatic versions of humanoids of some sort. Either goblins or hobgoblins.]
|One of the divers from Nemo's vessel captured by Gill-Men|